A true-blue Brooklyn organization, formed when the borough was the nation’s third largest city and when James Abram Garfield [1831-1881] was elected the 20th president of the United States, is still going strong — after 130 years.

The Society of Old Brooklynites, founded in 1880 by Mayor of Brooklyn John W. Hunter to help connect the business community, celebrated its milestone anniversary with a self-affirming installation of the Board of Officers of its 150 members at the Bay Ridge Manor on 76th St. between Fourth and Fifth avenues.

Life member Borough President Markowitz performed the June 27 honors, inducting Theresa Rosen, wife of late lawyer and top deputy to district attorneys in Brooklyn and Queens Norman Rosen, to her fourth term as president — 114 years after the organization first allowed a woman to join.

In its record of events for April 1896, the Brooklyn Daily Eagle Alamanac, confirms, “Mrs. Helen Dean, 102 years old, elected a member of the Old Brooklynites.”

His group helps link locals to their roots, said Second Vice President Ted General.

“Kids are taught world history, the nation’s history and state history in schools, but they don’t do such a good job of teaching about their neighborhood history,” said General, who was re-elected alongside First Vice President and former city Housing commissioner Myrtle Whitmore, Treasurer Sherman Silverman, Recording Secretary Linda Orlando and Corresponding Secretary Holly Fuchs-Ferguson.

That’s where the Society of Old Brooklynites comes in. Located at 340 Marine Ave. between Third and Fourth avenues, it continues to draw members — many of them not so “old” — who have lived in Brooklyn for at least 25 years, and who want to “help preserve the history of Brooklyn, to instill local pride and spirit, and to promote the borough’s cultural institution, literature and fine arts,” said General.

The venerable group, whose former members include American poet Walt Whitman [1819-1892], “father of baseball” Henry Chadwick [1824-1908], New York City’s 92nd mayor Seth Low [1850-1916] and US Rep. David August Boody [1837-1930], has been an integral part of New York history: It sent a delegation to the October 28, 1896 dedication of the Statue of Liberty, and another one when the Brooklyn Bridge opened to the public on May 24, 1883.

Today, the patriotic society is linked most closely to the Revolutionary War Prison Ship Martyrs Monument at Fort Greene Park, where it holds a ceremony each year to honor the 11,500 patriots who died aboard British ships at Wallabout Bay, between the Williamsburg and Manhattan bridges, and whose remains lie in a crypt beneath the memorial.

In 1888, the organization contacted the British War Office and obtained names of 8,000 American prisoners who were imprisoned on the jail ship Jersey. Fourteen years later, after securing a matching grant from Congress, it raised $100,000 to build a 148-foot-tall granite obelisk on the park’s highest point, enlisting the help of its illustrious membership under then-president Frank Spinner, and the Sons and Daughters of the American Revolution.

When it was dedicated by President-elect William Howard Taft on November 14, 1908, the memorial was the tallest, free-standing Doric column in the world.

More than a half-century later, a time span which would gobble up lesser organizations, the Society of Old Brooklynites continued its patriotic allegiance. On June 1, 1960 it installed a plaque above the monument on June 1, 1960, to honor the deceased sailors and soldiers.

The historic monument, said General, helped raise awareness about the “ultimate sacrifices” of America’s first Prisoners of War.